Justine Henin needed three hours to beat Slovenian qualifier Katarina Srebotnik and preserve her unbeaten record at the Dubai Championships.
Justine Henin was made to work very hard to preserve her record
The top-seeded Belgian surrendered a tense second set before closing out a 7-5 6-7 (6-8) 6-3 victory.
"That's the kind of match I need," said Henin after making the quarter-finals.
"It's never easy to have a bye and play a girl that has played a few matches. In the third set I felt the best I've felt in the last few weeks."
Third-seeded Serb Ana Ivanovic showed no sign of her recent ankle injury as she defeated Czech Nicole Vaidisova 6-4 6-0.
And Amelie Mauresmo will meet second seed Svetlana Kuznetsova in the quarter-finals after beating Japan's Akiko Morigami 4-6 6-1 6-4 in Dubai.
Mauresmo, who has slipped to 29th in the world rankings, is looking to reach her first semi-final since June but she faces a tough test against Kuznetsova.
The Russian world number two thrashed Lucie Safarova 6-1 6-2.
Despite her playing well and hitting the ball very solid I was also just struggling with my game
Fourth seed Jelena Jankovic needed more than two hours to see off India's Sania Mirza 4-6 6-3 6-4.
Mirza led 3-1 in the final set and had three points to make it 5-3 before Jankovic prevailed.
"She gave me a hard time on the court," said Jankovic.
"Despite her playing well and hitting the ball very solid I was also just struggling with my game."
The Serb now meets Anna Chakvetadze, who beat compatriot Dinara Safina 6-7 6-4 6-3.